Four-wire repeater circuits



2 shts-sheet 1 H. NYQUIST FOUR-WIRE REPEATER CIRCUITS Filed July 8,

L y l WJ O u J m E@ ww mm. wa @d .AQNNAN H. NYQUEST FOUR-WIRE REPEATER CIRCUITS Filed July 8, 1921 2 Sheets-Sheet 2 5140044160@ 52V 13j @51j @Hom/w12* Patented Dec. 29, 192.5.

UNITED STATES A 1,561,167 PATENT OFFICE..

HARRY NYQIST, 0F ELMHUBST, NEW YORK, ASSIGNB i RICN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK. A'

FOUR-WIRE REPEATER CIRCUITS- Application med vJuly 8,

To all whom t may concern:

Be it knownthat I, HARRY NYQUIs'r, residing at Elmhurst, .in the county of Queens and `State of New York, have invented certain Improvements in Four-Wire Repeater Circuits, of -which the following is a specification.

This invention relates to four-wire repeater circuits, and especially 'to a circuit arrangement for terminating Vfour-wire phantom circuits.

It is well known in the telephone art that a phantom circuit may -be derived from two physical circuits by means 'of suitably balanced retardation coils or repeating coils bridged across each end of each physical circuit and having a tap taken from the midpoint of each retardation coil or from the midpoint of the line winding of each repeating coil. Such circuit arrangements are designed forthe transmission of signals in both directions over each 'physical circuit and also over the phantom circuit.

, The so-called four-wire circuit comprises two pairs of ranged Yfor unidirectional signaling. In such a circuit, the signaling currents created at and` transmitted from one station will travel over one pair of wires to a second station, and similarly, the transmitted signals from the said second station will travel over a second pair of wires to the said first station. The term four-wire phantom circuit means a phantom circuit derived from two four-wire physical circuits. In such a phantom circuit, the signaling currents transmitted from onestation will travel over one pairof wires to a second station and will return over a second air of wires to the first station. The signa ing currents transmitted from the said second station will travel over a third pair of wires to the said rst station and will return over a fourth pair of wires to the said second station. It is necessary to have at each of the said stations connectedv with the four-wire circuits suitable terminating apparatus whereby the hantom circuit currents and the side circuit currents may be separated and directed into their proper terminal circuits at .each oi the said stations. necessary that the terminating apparatus shall befso arranged that the currents arriving over certain pairs or the four-wire circuits will not be fed back into other pairs wires, each of which 1s ar-v` It is alsoA of the four-wire' circuit, which would cause singing of the repeaters connected with thefour-wire circuitsA and thereby reduce the efficiency of transmission. p

My invention provides new arrangements for terminating which arrangements are characterized by the use of the minimum number of coil, thereby making the arrangement cheap an efficient.

Other objects of this invention will be apparent from lthe followin description, when read in connection with t e attached drawing, of which Figure 1 shows one form of embodiment ofthe invention; Fig. 2 shows an arrangement of the windings of the coils shown in Fig. 1; Fig. 3 shows a lvariation in the mode of bringing out the phantomA derived from two four-wire circuits, and Fig.

4 shows anotherform of embodiment of the terminal circuit havin a single network adapted to balance both the four-wire side circuits and the four-wire phantom circuit. In Fig. 1, pairs 1 and 3 constitute Ione :tour-wire circuit and pairs 2 and 4 consti tute a second four-wire circuit. Pair lcon-v stitutes the conducting path of the first four-wire circuit `in transmitting signals from station A to station B, yand pair 3 represents the conducting ath of the same four-wire circuit=in receivmg at station'vA signals transmitted' from station B. "For the purpose of brevity, these pairs will sometimes be referred to as the-transmitting and receiving circuits, respectively, of. the irst `four-wire circuit. Similarly, pair 2 represents the transmitting side of the second four-wire circuit and pair 4 represents the receiving side of the same four-wire c1rcu1t.

.In the designof fourfwirecircuits, in order to minimize cross-talk, all of the circuits transmitting energy in one direction between stations are grouped together and likewise all. of the circuitstransmittin energy in the'other direction are groupe to-v gether. 'Ihus in Fig. 1,- pairs 1 and 2, over which energy is being transmitted from lett to right between the repeater points are grouped together, the two pairs forming what'is designated as quad 1. In like inanner, pairs 8 ande, over which energy is being transmitted trom right to left are grouped together in quad 2. Each l,nad

constitutes one side or a tour-wire p an` ourfwire phantom circuits,

,sol

. four-wire circuit terminates, c1rcu1t currents and the side tom circuit and at the points where the the phantom circuit currents are directed'into their proper terminal circuits by means of a coil arrangement as shown in Fig. 1. e

Associated with each quad isa group vof repeaters adapted to amplify the currents of the physical and phantom circuits. Thus repeaters ,-Rl, R2 and R5, associated with quad 1, are' respectively adapted to ampllfy the currents traversing pair 1, pair 2 and the I'phantom transmitting circuit super-imposed upon the said pairs, and in like manner, repeaters R3, R and R6 are respectively adapted to amplify the currents traversing pair 3, pair 4, and the phantom r e ceiving circuit superimposed upon the sa1d pairs. The repeaters associated with quad 1 are all adapted to transmit energy 1n one direction, and the repeaters associated with quad 2 are adapted to transmit energy 1n the opposite direction.

The terminal circuit shown at the righthand side of Fig. 1 comprises five coils and three balancing networks. Coils' A and B serve in part to connect the four-wire circuit comprising pairs 1 and 3 with a twowire circuit v7, and similarly, lcoils C and D serve in part to connect the four-wire circuit 'comprising pairs 2 and 4 with a twowire circuit 8. Coil E serves to connect what may be termed the four-wire phantom c1rcu1t with the two-wire phantom circuit,

the latter made up of the two side circuits 7 and 8. The network N1 `is designed to balance the four-wire circuit 1 3 and similarly the network N2 is designed to` balance the four-'wire circuit 2-4. The network N 3 balances the phantom circuit super-y imposed upon the'said two four-wire circuits. By means of the repeating coils F and G, inserted in the physical circuits 7 and 8, the phantom circuit may be derived and terminated as the two-wire circuit 9.

The coils A and D, which are similar, are of the well-known type of phantom repeating coil comprising four windin s 1 2, 3 4, 5 6 and 7 8,arranged as siown in the figure. The relative arrangement of the windings upon the core of these coils is shown in Fig. 2. The four windings are put on.l inthe same direction and, consequently, it will be seen that if the current flows from the. odd numbered terminals to the even numbered terminals of the windings, the resultant flux will be in the same direction. Coils B and C differ from coils A and D in that in coils B and C the windings 5 6 are divided in halffthe reason for which will be made clear hereafter. The junction points between windings 3:4 and 7 8 of both coils A and D are connected with terminals 3 and 8, respectively, of coil E. In a similar manner, the junc- A vis connected' with the terminal 2 of coil` E and the midpoint of winding 5 6 of coilD is connected with the terminal 5 of coil E. The network N3 is bridged across themidpoints of windings l3 4 and 7 8 of coil E.l VVindings, 1 2 of coils A and B are connected in series with the balancing network N1. The terminals of winding 5 6 of coil A are connected to the inner terminals 5', 5 6 of coil B. -The outer terminals 5 6 of coil B are connected with the conductors of the two-wire physical circuit 7; In a similar manner, related to'coil C, sociation withrthe ancing network N2 cal circuit 8.

Hav-ing in mind the foregoing description of the parts of this circuit, the invention will be apparent from the lfollowing thereby bringing into asfour-wire circuit the baland the two-wire physidescription of the mode of operation of the.

circuit: let it be assumed that `energy is being transmitted from left to right over pair l, which is the condition'when a`voice signal is being transmitted from station A to station B. The current resulting therefrom may at any instant be v'assumed to be in the direction indicated by the solid arrows. Thus current will flow through the left-hand windin s of coil A in the direction represented y the numerals 4, 3, 8, 7. It will be seen byreference to Fig. 2, that the flux resulting therefrom will induce 1n the windings 1 2 and 5 6 an electro-motive force such as to cause current to flow in the direction represented by the numerals 1, 2,V 5, 6.` The current flowing in winding 1 2 of coil n'iinal 1 tovterminal 2 of winding 1 2 of 'coil B. The current flowing vin winding 5 6 of coil A will flow through the two halves of divided winding 5 6 of coil B in such direction as to set-up a flux which will oppose and neutralize the tlu'x set up by the flow of current through winding 1 2 of coil B. Consequently, no resultant current will be produced in pair 3, which'constitutes the other side of the same fourwire l circuit, and consequently .singing around the circuit, with its consequent loss 'of transmission, is prevented. The current which is set up in windingv 5 6 of coil A, flows through the dividedv Winding 5 6 of 6 of the divided winding` the'windings of coil D are A will likewise iow from teri coil B, and is in turn transmitted over the divided winding 6 of coil B, and also winding'5-6 of coil A. Let itbe assumed that the .direction of the flow of currentin circuit 7 is suchthat the current will pass from terminal 6 to 6 `and from 5 to 5. This will induce in winding 1 2 -of'coil B an electromotive force which will produce a flow of current from l'to 2. v.The flow of current in w'ndingof coil `A will be in Suchdireetion 'as to -cause an induced ilow of vcurrent from 2 to 1 of the winding 1 2 of coil A. vSince the Adirection of the flow of current in winding 1 2 of coil A is opposite to that of winding 1 2 of coil B, there will result no flow or current through the circuit containing the network N1.' The current -iowingthrough the-divided winding 5 6 of coil B will induce a current in the lefthand windings of the said coil, which vwill be transmitted through the amplifier R3 and, in turn, over pair 3 to station A. The current in winding 5 6'o'f coil A willalso induce current in the left-handwindings of the said coil, but in "view, o/f the unidirectional characteristic of the vacuum tube amplifier, this current will not pass through the .repeater'lt1 and, consequently, will netpass over the linejto station A.v The fourwire circuit made up of pairs2 and 4, over which voice signals'are transmitted from and re;A ceived at station'A, operates 1n the .same

manner as the previously described circuit,

and'the'voice signals originatingat stationA A, transmitted over the pair 2,-will be impressed upon circuitv 8 in such a manner as to prevent reaction upon .pair 4, so that .singing around the circuit comprising re- Y peaters R2 and IRI, is preyented. 'In theltransmission of voice signals fromA '40 station A to station B over the'phantom circuit, the resultant current will flow toward station B lover the two conductors of pair' 1- in parallel, as indicated byl the dashed arrows, and will return over the two conductors4 of .pair 2 in parallel,. as similarly indicated. The currentresulting from the transmission ofvoice signals from stationB `to station A, will -low Aover the two conductors of pair 3 vi`n paralleland'will return over the two conductors of pair 4 in parallel, as indicated by the dashed arrows. 'I he current flowing over the conductors of pair 1 1nparallel will 'pass through the left-'hand windings'of coil A from 7 to 8, and from 4; to 3,

whichzis in such direction as to prevent the induction of current in the right-hand windlings of the said coil. The phantom current will `flow` from the junction point 3 8 -over conductor 10 to terminal 3 of coilE, thence through winding Part of the current willlow through the network N, to the mid .y point 8"of winding 7 8 and thence to the junction .point 3 8 of the left-hand winding of coil D and over the conductors of pair 2 in'- parallel, to the source of current at stav bered terminals.

tion Since the direction of the flow ot4 current from the left-hand`windings ofcoil E is fromvthe odd numbered to the even numbered terminals, current will be induced in the righthand windings of the said` coil in the direction of the'even tothe odd num- Current will thus, How from terminal 5 of coil E-to the mid-poiiis of winding 5 6 of coil'D, then in paralleland in opposite directions through the dividedl winding 5 6 of coil C and over the conductors of 'circuit 8 to the mid-point of coil G,

thence to one side of the receiver associated wlth the phantom termlnating c1rcu1t 9.

The current will continue to flow through 'the receiverV of said phantom circuit to the midpoint ofthe winding of coil F, and thence over the conductors of circuit 7 in parallel to the terminals 5 and 6 of the divided winding 5 6, then in an opposite direction through the said windings tothe midpoint of winding 5 6 of coil A, vand over the conductor 11 to the terminal 2 of coil E. It will be seen that the flow of eurrent through the divided windings 5 6 of `coils B and C is in such directions as toi' prevent induction of currents in the lefthand windings ofv'coils B and C. Further-` more, there will be no flow of current over a circuit rom the-terminal .4 of coil- E to the junction point 3 8 of coil B and over pair 3 and pair i to the ljunction point 3 8 of coil C, to the terminal 7 of coil E, for the reason that the current that might .tend to flow over the latter traced circuit. due to its being in parallelwith the circuit through the network N3, is neutralized by the current induced in that portion-of the windings 3-4 and 7 8 lying between 3 and 4, respectively, and'8' and 7, respectively. by the flow of current through the network Ns. An analysis of these circuits will show that the direction of flow of current in the portions of the left-'hand windings of coil E stated above is such as to oppose the current which..

ings of the said coils being so arranged by a reversal of one oiLthe/coils `that currents traversing one pair of a four-'wire circuit will set upcurrents of the same magnitude in' the two-wire terminatin circuit, and also in. the balancing networ circuit. These .currents .traverse the windings of the re'- peating coil of thev other pair ofthe fourwire circuit in opposite ldirections and consequently, produce no resultant current in (he said pair, thereby preventing singing aroundv the circuit. This method of'connection makes it easyto superpose the phantom :so I

`- {wi-imposed uponL1 and 'L2 is related to `the circuit currents upontlie twoswirephantom circuit madeup of the pairs 7 andl 8.

Fig. 3 showsv an'arrange'ment wh'erebythe phantom circuit superimposedupon thetwof phvsical.fourfwlre circuits may be connected direct-ly with aphysical two-wire circuit by incline of the'right-hand Iwindings of 'coil E,

instead of being continued as aphantom ci r 'cuit' upon the .two-wire physical circuits 7 'and Sas shown inFig. 1.l

'41 showsan arrangement for deriving a ph .ntom circuitfroin two four-wire reymateicircuits, which employs three coils i :md a commombalancing network' instead of 'live coils and: separate networks as shown iufFig. 1. 'In the arrangement shown inlf`ig. 4." I1 and I2 represent two pairs of quad 1. and()1 and O2 represent two pairs of quad :2. l1 and O1 represent-the two sides of one four-wire circuit and=I2 and O2'represent 1he two sides of anotherj'four-wire circuit.

' l., and I2 constitute one side ofthephantom. circuit and O1 and O2 constitute the other' side of the phantom circuit superimposed,-

upon the two our-wire'circuits. Energy is transmitted iii the same direction, as indi-' .cated by the arrows, over pairs I,- .and` -I2 and also over the side of the phantom superimposed upon I1 vand I2; JInlike manner'v energy is transmitted in thesame direction over both pairs O1 and O2 and also over the -side o f the phantom super-imposed upon these two pairs, but the directionis opposite to that in which energy is transmitted over I1 and I2, and the side of thephanf tom super-imposed uponthese two circuits. Lt and L2 represent two two-wire `circuits which are related by means of windings ofwils-B and A respectively with the 4four-wire circuits, andlin likemanner the phantom su,

phantom superimposed "upon the two fourwire circuits by means of windings of coil C. Coil A, as' may be seen, embraces 'five windings, series with pair 1,; two with pair O1 and one. with pair L`2.- 'In a similar manner coil 'comprises 'five windings, two of which are connected in 'series with -pair I2, two with` pair O2 and one with pair L1. Coil em-v braces ten windings, four of which 'are ar.

i-'angedin series with pairs I1' and 0 four with' pairs I2 and O2' and two with pairs L'1 and L coil C,2associatedwith pairs' Il and O1', is a Connected with the windings of network- N2 adapted 'to balance'tliesaid pairs. and similarly connected 'with fthe 4windings associated withthe pairs I2 and 02 is a network N2 ada ted to balance the said pairs. Connected with the networks N1 and N 2 -:is a thirdiietwork Ns, which taken -Let-it be assumed that asi together with networks N1' and N 2, is adapted to balance the phantom circuit.

ahng wave is being 'transmitted'over 'pair 2 from station two of' which are connected in' A., and this'. wave isto be impressed'upon pair L2 for',transmission to a" station connected therewith. Current will flow through the windings and 7.-.-8 of coil A inthe direction indicated bythe arrows marked 1.

This current will also flow through windings 20-'19and '15'-16"of coil C and through the network N2' in the direction indicated by the arrows niarkedli- 'The difference of potential across 'the network N2 will of 'coursetend 'ioeausecurrent to flow through the windings 18-17ia`nd 13-14 yof c'oil C.' Since,

however, windings .9-10 and 11--12 of coil- A. lare iuducti'v'cly relat'ed\to the windings "5s-6 and---S .of the-samel coil,"a difference 'of potentialwill be set up in pair O1 which. willneutralizethe effect produced in windings 18-17 and 13e-'14 of coil C, thereby. preventing the transmission of energy out over pair O1 which prevents singingover the four-wire circuit represented by pairs I1 and O2. Current will however, .be induced in winding 144 of pair L2' and in this manner the energy-of the voice signaling wave oi pairfI1 will be'trans'mitted t'o the, station connected with pair Since the windings ci' coil C-and coils A' and kB'are arranged in the .niannersliown 'in Figure 2, in which theodd-numbers .represent one terminal of the windings and t e .even numbers represent ine -otherternnnal of the windings, current iowing in windings 2'0-'19 and 15-16 will produ'ceno -eti'ect in the other windings of this coil.

If -the station connected with the pairL2A desires to transmit, for example, a signal to Since the repeaters in'p'airI1 are adapted to transmit energy only in the direction Vrepresented .bythe` arrow,v noneof the' energy caused by' this. induced-potential can get through the repeaters. -On the-other'hand since 'the repeaters; connect'e'dff with pair 0 1, are Aadaptedtotransmit in the opposite direction, energy will bia-transmitted over pair' O1v tothe receiving apparatus v'connected with the 'four-wire' circuit at station AL. Y

The transmission 'of4 si' als in vopposite directions over pairs I2 an O2 representing the" other -four-wire circuit is accomplished 'byfineans of thel windings of coil B -in the saine mannerinwhich 'energy is transmitted over -.the four-wire' circuit represented b5 pairs -I1 and O2.

:Let 't te assumed'tha a Signal is 'to bf tra'nsn'ntted from station A over the phanton circuitsuperimpsed upon these two four wire circuitsfzY The current will ilow ovei in the appen will tend to iiowover phantom circuit.

the two wires of pair I1 in parallel as repre-v ings of coil A, and similarly no difference of potential will be induced in the windings of coil B by the' flowV of current through the windings5-6 and 8-,-7. Since the phantom current flows in the same direction through windings 20-19 and 16-*15 and returns in the same direction through windings 10-9 and 6*-5, there'willy be induced adil'erence of otential across winding l--2Y of coil C which will cause a'flow of current in the phantom circuit superimposed upon pairs L1 vand L2. It will also be seen that in transmitting ak signal from a station connected with the phantom circuit superimposed upon pairs L1 and L2 that no'current will beinduced in the side circuits of the four-wire circuits through the windings of coils A or B, but thatcurrentwill be induced in the phantom circuit superimposed upon the two four-wire circuitsby means of thewindings of coil C. This energy of the signaling wave the side of thephantom circuit superimposed upon pairs I1 and I2 and also over pairs O1 and O2. Since the phantom repeater associated with the side of the phantom superimposed upon pairs I1 and I2 is not adapted to 'transmit in the direction toward station A, the energy will not get throu h, consequently no detrimental eiect wil be produced. On- `the` the phantoml repeater asother' hand, since the side sociated with upon pairs O1 and O2 is adapted to transmit in the direction of station, the signaling wave will be transmitted to the said station and will 'be received thereby.

The aforedescribed arrangement provides a four-wire phantom terminating arrangef ment requiring only three transformers hav-` ing its balancing network so arranged as'to be capable of balancing both the four-wire physical circuits, as well as the four-,wire

Although this invention has been disclosed as having a particular form, it will be understood that it may be embodied in many other organization widely different fromV those illustrated, without departing from the spirit and sco e ot the invention als-defined ed claims.

What is claimed is:A

l. In a signaling system, the combination with one four-wire signaling circuit of a second four-wire signaling circuit, a twowirecircuit individual to eachfour-.wire Vcn'- cuit, a netwerkadapter! to balance each .of the said two-wire cucuits, and a plurality wire circuit circuits with superimposed four-wire circuits withV of repeating coils having their windings so n connected with the said four-wire circuits and with the said two-wire circuits and the balancing networks, cuit not only from the four-wire circuits but also from the two-wire circuits, l phantom circuit being thereby rendered electrically continuous.

2. In a signaling system, the combination with one tour-wire signaling circuit of a second four-wire signaling circuit, each fourbeing of the type in which the signaling energy for transmission'in one direction is carrled by one pair of wires, and

yfor transmission in the opposite direction is carried by the other pair of wires, and means to derive a phantom circuit from the said four-wire circuits. y f

3. In af signaling system, the combination with one 4four-wire signaling circuit of a second tour-wire lsignaling circuit, and means to derive the phantom circuit from the said four-wire circuits, said means comprising a plurality of repeating coils the windings of that the currentjn one branch of a fourwire circuit will not induce an E. M. F. in the other branch otthe same four-wire circuit.

4.. In a signaling' system, the combination with two four-.wire signalingcircuits-of two two-wire signaling circuits, a plurality of Anetworks individual to and adapted to balance the said circuits,` and a plurality of repeatmg coils connecting the said four-wire the said vtwo-wire circuits and as to derive a phantom cirthe said which are so 'interconnected their networks, whereby a continuous phan-v tom circuit may be superposed upon the said four-wireand the said two-wire circuits.

5. In a signaling system, the combination with two four-wire signaling circuits of two two-wire signaling circuits, a plurality of repeatingcoils adapted to connect the said the said two-wire circuits, whereby a phantom circuit may be superposed upon both the four-wire and the' two-wire circuits a d rendered electrically continuous, and a balancing network adapted to balance the two-wire circuits with res'pect to their use as physical circuits and as a phantom circuit.

6. In a signaling system, the combination with a four-wire repeater circuit com rising two pairs of conductors adapted' or the propa ation of signals thereover in opposite d1nection,'of a to balance the said two-wire circuit and a plurality of repeating coils `for connecting lthe said four-wire and the said two-wipe means, the sald so arran e four-wire circuit and said balancing) connecting repeating coils ein as to prevent singing over t circuit.

7. In a signaling with two four-wire repeater system, the combination circluts, each lll two-wire circuit, means having a two-wire terminal circuit individual thereto, of networks adapted to balance the 'said two-wire circuits, repeating coils adapted to connect each four-wire circuit 5 with its respective network and its twowire circuit, and another repeating coil and balancing network connected with both of said four-wire circuits and said two-wire clrcuits, `for effectively deriving a phantom .circuit from the said four-wire circuits. 10

In testimony whereof, I have signed my name to this specification this 7th day of July, 1'921.

. HARRY N YQUIST. 

